I'd write your speaker manufacturer and ask. Then I'd suggest you follow their instructions.
Virtually all flexible plastic and rubber compounds will stiffen and harden with age as the volatile organic compounds slowly evaporate. That is just a sad fact of life.
The catch is that applying compounds to protect the speaker's surround may not have the effect you intended. It might help preserve the surround. It might do nothing, or it could even accelerate deterioration.
If you get 14 years of life out of the driver before it fails when applying compound, would have that been 10 years without or 20 years? Short of applying the compound and seeing the speaker surround dissolve before your eyes you'll probably never know.
However, the real immediate danger is that applying a compound changes the compliance of the suspension and affects the sound of your driver. At that point, the driver that the designer so carefully selected to fit in that particular cabinet with that particular crossover is no longer the same. Your expensively acquired speaker no longer sounds as intended. That's probably the real reason to not apply anything to a driver unless you clear it with the speaker maker first.
Virtually all flexible plastic and rubber compounds will stiffen and harden with age as the volatile organic compounds slowly evaporate. That is just a sad fact of life.
The catch is that applying compounds to protect the speaker's surround may not have the effect you intended. It might help preserve the surround. It might do nothing, or it could even accelerate deterioration.
If you get 14 years of life out of the driver before it fails when applying compound, would have that been 10 years without or 20 years? Short of applying the compound and seeing the speaker surround dissolve before your eyes you'll probably never know.
However, the real immediate danger is that applying a compound changes the compliance of the suspension and affects the sound of your driver. At that point, the driver that the designer so carefully selected to fit in that particular cabinet with that particular crossover is no longer the same. Your expensively acquired speaker no longer sounds as intended. That's probably the real reason to not apply anything to a driver unless you clear it with the speaker maker first.